Means for minimizing inductive interference.



C. F. SCOTT.

MEANS FOR MlNlMIZlNG INDUCTIVE INTERFERENCE. APPLICATION FILED IMLZ. ms.

1 1 96,299. Patented Aug. 29, 1916.

1J E WITNESSES MENTOR W 0mm; [Jmfl CHARLES F. SCOTT, OF NEW HAVEN,

CONNECTICUT,

ASSIGNOB TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, ACORPORATION OF PENNSYLVANIA.

MEANS FOR MINIMIZING INDUCTIVE INTERFERENCE.

Application Med January To all whom it may concern:

Be it known that I, CHARLES F. SCOTT, a citizen of the United States,and a resident of New Haven, in the county of New Haven and State ofConnecticut, have invented a new and useful Improvement in Means forMinimizing Inductive Interference, of which the following is aspecification. My invention relates to means for m mmizing inductivedisturbances in electrical circuitsthat may be caused by other circuitswhich are located in proximity thereto.

More particularly, my invention is applicable to the protection oftelephone, telegraph and other circuits utilized for the transmission ofintelligence which are very susceptible to inductive disturbances andare paralleled, for longer or shorter distances, by circuits utilizedfor the transmission of power by alternating currents.

When telephone, telegraph and like circuits are in proximity to circuitscarrying alternating currents for lighting or power purposes, such asalternating-current railway systems, the electromotive forces induced inthe intelligence-transmission circuits disturb and frequently precludetheir successful operation. Consider, for example, analternating-current railway system in which a trolley wire constitutesone of e supply conductors, and the track rails, either alone or inconjunction with the ground, constitute the other sup 1y conductor. Whena moving vehicle receives power from the system, a primary circuit,comprising a single convolution of varying length, is formed which mayinduce alternating electromotive forces in a secondary circuit, as, forinstance, a telephone or telegraph circuit that is located partially orwholly in proximity thereto.

The electromotive forces induced in the secondary circuit depend uponthe distance between the intelligence transmisslon system or secondarycircuit and the railwa system. or primary circuit, the amount an rate ofvariation of the current flowingl in the rimary system and the lengthoft e secon ary circuit which is in the zones of disturbing influences.If a continuous trolley is employed and it receives current from severalsubstations, then a car or locomotive will re= ceive current, not onlyfrom adjacent sub= stations, but also from those which are re= mote fromit. The current from the more Specification of Letters Patent.

Patented Aug. 29, 1916. 2,1915. Serial No. 168.

distant sub-stations will be parallel to the secondary circuit for avery considerable distance, and will, therefore, induce a much greaterelectromotive force than would resultif the whole, or-a much largerproportion, of the current came from adjacent substations.

Disturbances in the secondary, or telegraph circuit may be minimized ifthe proportion of the current which is supplied by remote sub-stationsis reduced. ccording to my present invention, I propose to minimize theelectromotive forces induced in adjacent intelligence-transmissioncircuits by limiting, to a small amount, the current flow from thosesub-stations which are remote from the moving vehicle.

For a better understanding of the nature and scope of my invention,reference may be had to the following description and the accompanyingdrawing in whlch the single figure is a diagrammatic representation of arailway system embodying a continuous trolley and equipped with myinvention, by means of which the inductive disturbances in a telegra hline paralleling the railway system may e minimized.

An alternating current generator 1, which, for simplicity, isrepresented as a singlephase generator, supplies power, through astep-up transformer 2, to distributing or feeder conductors 3. A seriesof sub-stations. represented by transformers 4, 5 and 6, are connectedto the high-tension feeders 3 and transfer power at the desired voltageto a continuous trolley conductor 7, which, in turn, furnishes power toa traveling vehicle 8. Located in inductive proximity to the trolleyconductor 7, is a conductor 9 of an intelli ence transmission system,such, for cramps, as a telegraph system.

Becondary windings 10, 11 and 12 of the transformers 4, 5 and 6,respectively, are connected, at convenient intervals, to midpoints ortaps 13 of impedance devices or coils 14-.-15--16. The impedance coilsare connected, at corresponding intervals, in series relationshi withthe trolley conductor 7, thereby divi ing the railway system into aplurality of sections over which one or several vehicles may travel. Theother terminals of the secondary windings 10, 11 and 12 are connected tothe track 17, which comprises the return conductor for the trolleycurrent.

When there are a number of substations feeding the trolley. andenthesame the vehicle, eurrentsw ill bef upplie from each of them, theamount of current flowing from remote sub-stations I. beingrdeterminedby the relative impedances of the sub-station transformersandplithetrolley circuitw If 'the impedance offered by the trolley tothe current snppliedtdthe vehicle 'flows'in one directlon and,therefore, no oppesmg 'elece tromotive forces are inducedin theconductor 9' such as would re t if'the"vehicle received currentfrombotlidii'ectidns. i

In my system, when current is delivered to the movingv vehicle fromasub-station immediately adjacent thereto, it will be im peded by onlyone-half'of the impedance offered by the impedance coil directlyconnected to the said sub-station. The fl w of active coils whichareins'ert'ed I tions of the trolley along which "such currents tend toflow, and the current will, therefore, be impeded and reduced in amount.Each designed that the impedance to the flow'of current from thesubstation at which the coili's located, is missible limits, but theimpedance offered to the flow of current from remote sub-stations issubstantially high,'thereby precluding the flow of large quantities ofcurrent for lzong distances along the trolley conductor are suppliedequally, in each direction, to adjacent railway sections, themagnetizing effects of the equal currents flowing in opposite directionsaround a core 18 of the impedance device 15 will neutralize each otherand, therefore, permit the trolley currents to flow unimpeded from theintermediate sub-station in the two adjacent railway sections.

s above mentioned, the inductive disturbances impressed on the conductor9 are dependent upon the amounts of current flowing in the trolleyconductor 7, and also upon the distances over which these currents flow.Therefore, I limit the current flow from remote substations tosubstantially low values by means of the impedance devices 14-1516 andthereby decrease the intensity of the disturbing influences upon theintelligence-transmission conductor 9.

in"th atada ts 9- operation 7 within 5 per- If currents from thetransformer 5 the entire" length of At the same time, the trolleyconductor 7 may be maintained continuous throughout the railway system,power being supplied to the trolley conductor by means of a plurality ofsub-stations. While the intelligence-transmission circuit maybeinductively related, to the trolley the railway "system, the inductivedisturbances imposed thereupon are greatly minimized by means of myinvention. I cla'imas my invention: p 1. Means for minimizingelectromagnetic inductive disturbances between parallel conductorscomprising an impedance coil conthe inducing conductor,

in series with a source ofalternatlng-current supply, and

terminal only OfSaId source is connected to said inducing'conductor.

' said source is connected at a plurality of of the coils 14- 15 16 isso said points to said inducin conductor.

Means for minimizing electromagnetic inductive disturbances betweenparallel conductors comprising a plurality of spaced impedance coilsconnected in series relationship with the inducing conductor, a sourceof alternating-current supply, and conductors connected to mid-points onthe impedance coils whereby one terminal only of source is connected ata plurality of points to said inducing ('ldllCtOl'.

4. Means for minimizing electromagnetic inductive disturbances betweenparallel conductors comprising a plurality of spaced impedance coilswhich are connected in series circuit with the inducing conductor,intermediate taps upon said impedance coils so spaced as to neutralizesubstantially the impedance of said coils when equal currents flowtherefrom in opposite directions, a source of alternatin -currentsupply, and conductors connected to said intermediate taps whereby oneterminal only of said source is connected at a plurality of points tothe inducing conductor.

5. cans for minimizing electromagnetic inductive disturbances betweenparallel conductors comprising a plurality of spaced impedance coils ofnormally high impedance which are connected in series circuit with theinducing conductor, an intermediate tap upon each of said impedancecoils whereby the impedance thereof may be substantially lowered whenequal currents flow therefrom in opposite directions,

conductor throughout the length of one terminal only of a a source ofalternating-current supply, and a conductor conratio flow therefrom inopposite directions, nected to each of said taps whereby one tera sourceof alternating-current supply, and 15 minal only of said source may beconnected a conductor connected to each of said taps to the inducingconductor. whereby one terminal only of said source is 6. Means forminimizing electromagnetic connected at a plurality of points to theininductive disturbances between parallel conducing conductor. ductorscomprising a plurality of spaced im- In testimony whereof, I havehereunto zo edance coils of normally high impedance subscribed my namethis 23rd day of Dec. which are connected in series circuit with 1914.

the inducing conductor, anintermediate tap CHAS. F. SCOTT. upon each ofsaid impedance coils whereby Witnesses: the impedance thereof may besubstantially B. B. Hmns,

lowered when currents of predetermined M. C. Mnnz.

